There are two main types of infrared sensor. 1) Thermoelectric sensors, and 2) quantum sensors. Thermoelectric sensors are superior to quantum sensors because:
1. They are able to operate at room temperature; Quantum sensors require a low temperature environment between -100.degree. C..about.-200.degree. C. to operate. PA1 2. Rapid response; Response time for thermoelectric sensors is faster than that for Golay cells (see Computers & Telecommunications, Volume 21, p.265, M. Okuyama, 1985).
Referring to Addison Wesely (John P. Uyemura, p.21 Chapter 1) reveals that traditional thermoelectric FETs which use surface channel designs suffer from scattering on the transistor surface and traps created during fabrication which reduce mobility.
According to M. Okuyama(Computers & Telecommunications and Ferroelectrics volume 63, p.243, 1985), the rise time of traditional thermoelectric FETs is 3.5 .mu.S and electrical current is less than 1 .mu.A. As direct switching is not possible, an amplifier is required, which delays switching time.